Die



June 17, 1941. G, D, ROGERS 7 2,245,608

DIE I Filed Dec. 19, 1938 I 8 H I 4 ll l0 l2 IHVETL L m EEUFQEL DJEHEFE21 W; Max

A L L 1: vruays Patented June 17, 1941 UNITED sT Ts-s George D. Rogers,United States Army, Picatinny 7 Arsenal, N.

Application December 19, 1 938, S eria1 nogziaeis (Granted under the actof March 3-, 1883, as amended April 30, 1928; 370 0. G. 757) 1 Claim.

The invention described hereinmay be manufactured and used by or for theGovernment for governmental purposes, without the payment to me of anyroyaltythereon. I

This invention relates to an improved die for use in the granulation ofsmokeless powder or extrusion or squirting of similar plastic materials.

It has been a commonplace practice in the art, heretofore, 'to use steeldies 'for granulatihg or grain-mg smokeless powder, however, dies madeof steel are not entirely satisfactory owing to the abnormal variationsinfgrain' dimensions and other marked irregularities in'the grainseffected through wear 'of the die after a short period of service. Asuniformity of grain dimensions is essential to uniformity of ballisticperformance it is necessary to frequently exchange dies to avoidthevariation in grain size effected by" worn dies and depend on blending togive a lot of powder having grains conforming, within slight permissibletolerance, to the mean dimensions of a certain specified number ofgrains of the'lot selected at random for purposes of this physical test.Inasmuch as experience has amply demonstrated that blending in itself,no matter how long continued, will not insure the high degree ofballistic performance'required of a lot of powder, if grain dimensionsare abnormally variable, it isimperativethat the die dimensions remainconstant or within small tolerable limits. Moreover the wear on dies inthe extrusion of reworked unstable powder is considerably greater thanthe wear on dies in the extrusion of the regular colloid which isreflected in the unit cost of the reworked powder through increased diereplacement cost.

It is an object of this invention to increase the uniformity of graindimensions of powder granulated by extrusion through employment of dieshavinga maximum wear and corrosion resistance. For this purposeindustrial jewels, natural or synthetic, are admirably adapted ifmounted in a proper die body or holder.

While the use of industrial jewel dies, particularly diamond dies, iswell known in the wire drawing art for reducing the stock being drawn,there is no appreciable transverse flow of the stock and no confinementof the original stock except at the die opening, which presents a verydifferent problem in mounting the jewel compared to the one presented inmounting a jewel die for expressing a plastic material where the mass ofmaterial must be confined on all sides and at all points under highpressure except at the die opening. v 1 It is a further object of this;invention to so form thedi'e and die body or holder'that shearing stresson the die body or holder will be'd'i-stributed in a manner to eliminatethe tendency of the foundation or support in the die body for the die todeform and thereby subjectthe die to bending strains of a magnitudes'u'fiicient to crack the jewel die. The specific nature of theinvention as well as other objects 'and advantages thereof will clearlyappear" from a description of a preferred embodiment as shown in theaccompanying drawing in which: a Fig. 1 is a vertical sectional Viewthrough the die and die'body or holder in assembled relation; Fig. 2 isa top plan view of the die assembly; Fig. 3 is a vertical sectional viewsimilar to Fig. -1 showing a modification. Referring" now to thedrawings by character of reference wherein the same characters identifythe same, elements throughout the views there is shown inFig. 1 a diebody or holder l.' The diebody I may be made from an elongated steel dieblank of conventional form and is externally threaded at 2 for thepurpose of facilitating its attachment to a powder graini'n'g press heador: similar plastic pressing mechanism. For

the purpose of mounting a jewel. die 8 within the: die. body I thelatter is" cylindrieally bored longitudinally of its axis on twodiameters, stepped relative to each other, to provide axial cylindricalbores 3 and 4' joined by an annular ledge or abutment 5. The ledge orabutment 5 is made as nearly a plane surface normal to the axis of thedie body I as possible and likewise the surfaces defining the bores 3and 4 are made as nearly cylindrical as possible for reasons hereinaftermade apparent. A third cylindrical bore 6 of smaller diameter than bore3 is made in axial prolongation of bore 3 to provide a second annularledge or abutment I and to also complete the axial passage through thedie body I. The ledge or abutment I is made as nearly parallel to theledge 5 as possible.

The die 8 consists of a suitable jewel, such as natural or syntheticsapphire, or agate, shaped to provide an elongated annular die bus-hing9 and die cup Ill. The bushing 9 is of an axial length conforming to thecorresponding distance between ledges 5 and l and has an outsidediameter slightly greater than the diameter of bore 3 at normaltemperature. The die cup III in the form shown in Fig. 1 is madeintegral with the bushing 9 and is suitably shaped interiorly of itsperiphery to provide a funnel shape cavity I I terminating in an orificel2 forming a prolongation of the axial passage I3 in die bushing 9. Thediameter of the die cup I is also of slightly greater diameter than thediameter of bore 4 at normal temperature and its peripheral surface isjoined to the peripheral surface of die bushing 9 by a plane surf-ace I4made as nearly normal to the axis of orifice I3 as pos-" sible. The endof die bushing 9 remote from die cup III is provided with a. planebearing surface I5 also made as nearly normal to the axis of orifice I3as possible.

The precaution of making surfaces 5 and I of the die body I and surfacesI4 and I5 of the jewel die 8 plane and parallel to each other when thedie 8 is positioned in the die body I is to insure as nearly perfectbearing relation between cooperating bearing surfaces I--I5 and- 5-H asis possible so that the jewel will not be subject-ed to bending strainsupon application of pressure in extruding.

In assembling the jewel die 8 in the die body I the die body is firstheated to a temperature to expand the bores 3 and 4 sufficient to permitthe insertion of the die 8 within the bores 3 and 4 as shown in Fig. 1after which the die body is shrunk upon the die by cooling, which placesthe die under compression and the die body in tension transversely oitheir respective axes. The magnitude of compression under which thejewel die is originally stressed will be governed by the workingpressure to which the die is subjected, and will be greater than suchworking pressure so that the die will not be expanded beyond theaccuracy desired in the diameter of the extruded material.

As shown in Fig. 1 the axial passage I3 of die bushing 9 and orifice l2of die cup II] are of cylindrical form and have their axes coincidingwith the axis of die body I but it is understood that the extrudingpassage in the die. 8 may be of any suitable shape and that likewise thecavity I I in die cup I0 may be modiiied to suit it for use with anyparticular plastic material being extruded.

It will be observed that because of the frictional engagement betweenthe outer surface of the die 8 with the cooperating surface of the diebody I that the stress on the ledges 5 and I in the body are reduced andhence the shearing action in the metal of the die body I as seen belowthe steps 5 and I in Fig, 1 is minimized with the result that thisportion of the die body will not be deformed and the jewel will not besubjected to bending strains. It will also be observed that the die cupIn is supported by a comparatively long extent of metal in the die bodyI below the ledge 5 as seen in Fig. 1 which gives a more substantialsupport for the die in that region where the total pressure actingthereon is greatest.

In the form shown in Fig. 3 the jewel die 8 consists of a die bushing 9'and die cup I0 made as separate parts. By this arrangement it ispossible to use a die bushing made of one character jewel and a die cupmade of another character jewel whereby jewels may be selected for usein the die which collectively give combined characteristics desired butnot attainable in a single jewel. Moreover, another important advantagelies in the fact that the die cup may be replaced independently of thedie bushing. It will be observed that the accurate dimensioningandfitting is of importance to adequately support the die cup I0? partof which engages the ledge 5' and the remainder I the jewel bushing 9'.

In both forms of the invention the stock of metal surrounding the bore'6 is sufiicient to provide a seat I5 of suitable shape for a tool toexpedite threading the die into the press head.

Having now particularly described What is at present regarded apreferred embodiment of this invention I claim and desire to secure byLetters Patent of the United States:

. A powder extrusion die comprising in combination an elongated die bodyhaving an axial passage the-rethrou-gh formed by at least threecylindrical bores of successively stepped diameters, said bores beingjoined at their contiguous ends by annular ledges having plane surfacessubstantially normal to the axis of the passage, a jewel die disposedwithin the two bores of lar est diameter comprised of an annular diebushing having a plane end bearing surface engaging the annular ledge ofsmallest diameter and an annular die cup of greater diameter having aplane bearing surface extending outwardly from the periphery of the diebushing engaging the other annular ledge joining the two bores withinwhich the die is disposed, said die being circumferentially engagedthroughout its length by the die body under substantially uniforminherent pressure.

GEORGE D. ROGERS.

